Indonesian Pit Viper

Trimeresurus hageni, commonly known as Hagen's pit viper, is a venomous species within the Viperidae family, specifically the Crotalinae subfamily. This snake is indigenous to Southeast Asia and currently has no recognized subspecies. The species name "hageni" honors Dr. Bernhard Hagen, a German naturalist celebrated for his extensive wildlife collections in Sumatra.

Hagen's pit viper exhibits distinct physical characteristics. Typically, it possesses 21 rows of dorsal scales at midbody, between 176 and 198 ventral scales, 63 to 89 subcaudal scales, and 9 to 12 supralabial scales.

Geographically, this species is found in Peninsular Thailand, Peninsular Malaysia, East Malaysia (Borneo), Singapore, and Indonesia (including Sumatra and adjacent islands such as Bangka, Simeulue, Nias, Batu, and the Mentawai Islands). Originally, the type locality was recorded as "Sumatra.. island of Banka" but in 1933, Brongersma refined this to "Deli, Sumatra."